Implement a LogMiner event buffer SPI

It would be useful to introduce an SPI that allows events read from LogMiner to be managed in different ways such as:

• An in-memory buffer like what the connector currently uses
• A JCache backed buffer that can be persisted
• A JDBC backed buffer that can be persisted in the local Oracle database or a remote database (followed up by DBZ-3798)

The LogMiner event buffer SPI is meant to address a few concerns:

• Allow advancing the SCN values in offsets more regularly
• Handle long-running transactions without memory overhead when using persist backed buffer solutions
• Allow resuming the connector with SCN offsets that are closer to real-time when events are persisted via the buffer
• Allows using certain techniques to perform bulk operations more easily on data, i.e. JDBC backed buffers would allow bulk record filtering & processing